An electronic device may be, for example, a wristwatch. This watch is formed of mechanical and electronic parts, which generally require protection from water or moisture or various gases in the environment. Leak detection, generally of gas, has to be performed to determine a degree of sealing of the watch and mainly of the case containing all the watch components. This degree of sealing is normally determined when the watch model is designed, i.e. according to the thickness of the case with the watch glass and sealing gaskets.
The watch sealing measurement can be defined as a pressure calculated in atm or hectopascals. Different degrees of sealing can be defined. For example, for hand washing with a watch worn on the wrist, the watch must be capable of withstanding a pressure of around 3 atm, which is equivalent to a pressure of around 3040 hectopascals. To take a shower or swim in a pool with the watch, the watch must be capable of withstanding a pressure of around 5 atm, which is equivalent to a pressure of around 5066 hectopascals. For diving in a swimming pool, the watch must be able to withstand at least 10 atm pressure, which is equivalent to a pressure of around 10133 hectopascals.
There exist various seal checking instruments particularly electronic devices in the form of watches having a case. It is known to use an instrument which operates using compressed air to perform the seal test. It is possible to observe, for example, whether the watch crystal deforms when the watch is placed under pressure. If the watch crystal deforms, this indicates that the watch is well sealed, whereas if no deformation is observed, the watch is not considered sealed. This type of compressed air instrument permits a watch to be checked in similar conditions to those of normal use. An example of this type of checking instrument is one of the instruments sold under reference SM 8850-XX by Sigma Electronic SA in Bienne, Switzerland.
However, with every known type of seal checking instrument, this complicates the method of guaranteeing the proper sealing of an electronic device, such as a wristwatch. The seal checking costs for each electronic device are therefore high. Generally speaking, there is nothing provided in the state of the art to enable leak detection to be performed for an electronic device with means peculiar to the electronic device, which is a drawback.
JP Patent Application No. 2010-151656, which discloses a device for diagnosing the sealing of case, may be cited. An atmospheric pressure sensor is disposed in the case for determining the variation in pressure if a leak is detected through the case. However, this type of device cannot determine the variation in pressure outside the case and take account thereof in diagnosing the sealing of the case, which is a drawback.
EP Patent Application No. 1 388 766 A1 also discloses a device for checking the sealing of a sealed watch case. To achieve this, a pressure sensor is disposed in the case for determining pressure variations inside the case, but the invention does not provide for normal external pressure variations to be taken into account, which is a drawback.